The reason you take the musicians in the units of Dragon Princes is so that you can flee from a charge and rally on 10 and less (ie. only fail 1 in 12 tests, significant improvement over 1 in 6) in the event that someone tries to charge them with something that might actually break them without the +2S lances available to you.
This is particularly handy for setting up a situation where your opponent has to charge one of the two units or get wrecked. You flee with the one he attempts to charge, the opponent's unit has a failed charge. Your other Dragon Prince unit now gets to counter-charge, and if you've set it up correctly, often the counter-charge will be flank. In the meantime, you use your wonderful musician to make sure you rally your fleeing Dragon Princes, and depending on how you're set up, you should be protecting the flanks/rear of the engaged unit in case something bad happens.
But if you are planning on taking a Noble with each unit, I imagine that you aren't planning to try and set traps, and you'd rather just plow full-speed ahead into anything you think you can break in one round of combat with a normal front charge.
Just keep in mind that the Chariots can't march move, so they are going to be even slower than the White Lions I am assuming they are guarding the flanks of, especially if you set them out wide to maximize your angles of coverage.
The only thing I'd be moderately concerned with is the size of that White Lion unit. It's a little small for guarding a caster. The first problem with this is that once he kills 5 of them, you no longer have targeting protections or Lookout Sir! (your champion doesn't count as rank-and-file, and you need 5 rank-and-file to have these work). That makes your Archmage very vulnerable.
The second, and arguably more serious, problem with a 10-man unit is that even if you go to 6 wide in front with the mage sitting on the end, most opposition units are going to be wide enough to force it into base with 2 models. A smart opponent won't bother to challenge you with just a champion since you'll refuse and send the Archmage to the back, and if one of those two models in case contact with your Archmage happens to be a champion or character, he'll simply kill the archmage that way (overkill points for CR won't matter if he kills your Archmage in CC before the last turn or two, you've probably already lost the game unless he screwed up real bad somewhere else). Even just two regular troopers in base are more than likely going to rack up at least one wound, more if they have multiple attacks each.
To be honest, I don't see anyway to fix that problem though without seriously altering your list. The White Lion unit really needs to be bigger, preferably 13 or 14 so you can go 7 wide and ensure maximum of one model in base with your Archmage and zero in base against some units, but I don't see anywhere you can easily cut points except the Amulet of Light, but I assume you need that so that you can have a unit to deal with Ethereals or to wipe off Daemonic (or equivalent non-magic ward) saves.
